Telephone system



Oct. 13,1925

1.. b. KELLOGG TELEPHONESYHfil Filed Sept. 19. 1921 Patented Oct. 13, 1925.

UNITED STATES LEROY D. KELLOGG, O'F DEERFIELD, ILLINOI'S ASSIGNOR T'O- KELLOGG SWITCHBOARD PATENT OFFICE.

AND SUPPLY COMPANY, or CHICAGO, ILLnvoIs, A CORPORATION or ILLINOIS.

TELEPHONE SYSTEM.

Application filed September 19; 1921. SeriaI No. 501,752.

T 0 all whom it may concern:

Be it known that I, LEROY D. KELLOGG, a citizen of the United States of America, resident of Deerfield, in the county of Lake and State of Illinois, have invented certain new and useful Improvements in Telephone Systems, of which the following is a specification. I

My invention relates to telephone systems in which manual link or cord circuits are provided for interconnecting telephone lines, and has to do more particularlywith so-called multiple line lamp systems in which automatic listening, secret service, automatic ringing, dark key shelf, etc., are provided, and has for its object a new and improved system of the above character.

A feature of my invention is the provision of a new and improved link or cord circuit-wherein an audible busy-back sig nal is connected to the cord circuit upon the insertion of the calling plug into one of the multiple jacks ofthe called line upon which jack there is a busy potential due to the called line already being in use. In my invention I provide a cord circuit and a busy-back signal which I have so arranged that the operator is not required to test the multiple jacks of the called line to determine their busy or idle condition before inserting the calling plug of the cord circuit into the multiple jack of the called line as in the prior systems; but in my inventionwhen the operator learns the want of the called subscriber she inserts the calling plug of a cord circuit into the multiple jack of the desired called subscriber without making the usual preliminary busy test of the multiple jacks. Should therebea busy potential on the said multiple jacks, a relay is operated to connect a busy-back signal in circuit with the calling substation to indicate to the calling subscriber by an 1 audible sound that the called line is busy whereupon the calling party replaces his receiver upon its switchhook, which causes both theanswering and calling supervisory lamps to light, thus notifying the operator to take down the connection; but should there be no busy potential upon the said multiple jacks, the said relay will not operate and ringing current will be automatically and intermittently applied to the call bell of the called substation. f I

Another feature o-finy invention is th absence of a ringing key and the provision of a ringing circuit arrangement wherein ringing current is automatically and instantaneously applied to the called substation upon the insertion of the calling plug into the calling jack, providing the called line is idle, without the assistance of the switchboard operator.

For a more complete understanding of my invention, reference may be had to the accompanying drawing in which I show a well-known common battery substation A connected by line limbs 1 and 2 to a line circuit L. Multiple jacks J are distributed among different operators, each multiple jack having a line signal S associated thereanswering end of the cord circuit C is the double wound answering supervisory sleeve relay. AS; which is energized in series with the cut off relay C0 of the line circuit L when the plug AP isinserted into the jack J. Supervisory sleeve relay AS energizing,

connects the operators telephone set to the cord circuit C and closes a locking circuit through one of its upper alternate contacts, thus shunting out its upper high resistance winding which prevents a second operator from seizing the call, as will be more fully explained in the ensuing specification. An answering supervisory tip relay AT and an answering supervisory lamp AL are also shown, the relays AS and AT controlling the circuit of said lampAL.

Associated with the calling end of the cord circuit C is a sleeve relay CS which energizes upon the insertion, of the calling plug GP into the-multiplerjack J of the line circuit L. I also show a busy test :relay BT and a busy back control relay BC, saidbusy test relay BT energizing to prevent the operation of relay BC from connecting busy-back signal BB to the cord circuit in case the calling plug CI is inserted in a multiple jack J free from busy potential, but in case the said multiple jack J has a busy potential thereon, re-

lay BT will fail to energize thus permitting the relay BC to energize to connect the busy back signal BB to the cord circuit C, as will be more fully hereinafter described.

A ringing generator G, interrupter relay IR and interrupter I are also provided for automatically and intermittently applying ringing current to the call bell of the called substation D. I also show a ringing trip relay RT which operates to close an energizing circuit for the ringing control relay RC. Should the called subscriber respond during a ringing period, relay RC operating disconnects the ringing currentfrom the called line. I also show a calling supervisory relay SR and a calling supervisory lamp CL, said relay SR controlling the circuit of said lamp CL. Relay SR energizes upon the removal of the receiver from the switchhook at the called substation D and should this removal of the receiver occur during a nonringing or silent period, it is obvious that relay RC will energize to disconnect the ringing current from the called line.

To the right of the drawing I show a called substation D connected by the line limbs 1 and 2 to the line circuit L similar to that of L and having the same reference characters, but with the suffix prime added.

Having described in general the apparatus embodying my invention, I will now describe in detail the operation of the system as illustrated.

Assuming that the subscriber at the substation A initiates a call, the removal of the receiver thereat closes a circuit for the line relay LR traced from battery, through the winding of said relay LR, normal contact 5 of the cut oil relay CO, line limb 1, through the now closed contacts of the raised switchhook of the substation A, line limb 2, normal contact 6 of relay CO to ground. Line relay LR energizing closes its alternate contact 7 which causes the multiple line lamps S to burn over a circuit traced from battery, through the signals S, alternate contact 7 of relay LR to ground and other side of battery. An operator noting the burning line signal will insert the anwering plug AP of the cord circuit C into the multiple jack J, whereupon answering supervisory sleeve relay AS energizes in series with the out off relay C0 of the. line circuit L over a circuit extending-from battery, through both windings of relay AS, sleeve contacts of the plug AP and jack J to ground throu h the winding of cut ofl relay CO. Cut oil relay CO energizing opens its normally closed contacts .5 and 6, thus permitting the restoration of the line relay LR whereby the line signals are ellaced. Upon the relay AS energizing it closes its alternate contacts 8, 9, 10, 11, 12 and 13, thus connecting the operators telephone set 0 to the talking conductors 3 and a of the cord circuit CO, the re upper winding of relay AT, conductor 3,

alternate contact 8, of relay AS, tip contacts of plug AP and jack J through the calling substation A, ring contacts of plug AP and jack J, alternate contact 13 of relay AS, conductor 4, to ground through the lower winding of relay AT. Relay AT energizing prevents the premature burning of lamps AL and CL thus providing a dark key shelf.

Before proceeding further with the description of the connection, I will describe briefly the arrangement for excluding operators who may subsequently attempt to answer the call from the same line. Assuming that a second operator inserts aplug AP into another jack J of this calling line, subsequent to the insertionof the first plug, this second operators telephone will not be connected to the calling line, since the upper high resistance winding of the sleeve rela AS of the second cord is connected ,in muf tiple with the sleeve relay AS of the first cord, which relay, having its upper high resistance winding shunted, shunts the sleeve relay of the second cord and prevents it from actuating, thereby preventing the ope-rators set of the second cord from being connected to the cord circuit and calling line. The second operator not receiving any reply to her inquiry will know that the call has been seized by another operator.

Again taking up the first connection, the operator, after learning the want of the calling subscriber A, and assuming that he desires a connection with the subscriber at substation D, and further assuming the called line to be idle, will without testing the multiple jack J to determine its idle or busy condition, as is the usual practice, insert the calling plug CP into the jack J whereupon the calling sleeve relay CS is energized in series with the cut off relay C0 of the line circuit L over a circuit traced from battery, winding of relay CS, line H, sleeve contacts of plug GP and jack J to ground through the windin of cut off relay CO of line circuit L. Telay CS energizing disconnects the operators telephone set 0 from the cord circuit at contacts 15 and 16 which are now open, while out 01f relay CO energizing opens its normally closed contacts 5 and 6 which will prevent the line signals S from lighting when the sub seriber at the called substation removes the receiver from the switchhook. When the plug CP was inserted into the jack J, an energizing circuit was established for the double wound busy test relay BT extending from battery, through both windings of said relay BT, normal contact 19 of the busyback connecting relay BC, sleeve contacts of plug CP and jack J to ground through the cut off relay CO. Relay BT energizing shunts out its upper high resistance winding and closes a locking circuit for itself through its alternate contact 24L and lower winding and overthe previously described circuit. Relays CS and BT now provide busy potential to the multiple jacks J of the called line, thus rendering them busy against incomingcalls. The opening of normally closed contact 25 of relay BT opens a contact in the energizing circuit for relay BC before the latter has time to energize, thus preventing its operation to connect the busy back signal BB in circuit with the calling substation A. In terrupter relay IR will now energize and tie-energize to intermittently connect ringing current to the called line, the circuit being traced from battery, through the winding of said relay IR, alternate contact 23 of relay BT, normal contact 28 of ringing control relay RC, through the live segments of the constantly rotating interrupter I to ground. The ringing current circuit i11- cludes the circuits of battery B, alternate contact 30 of relay IR, ring contacts of plug CP and jack J, linelimb 2, call bell and condenser of the substation D, line limb 1, tip contacts of the plug CP and jack J, alternate contact 31 of relay IR, winding of ringing trip relay RT, generator G to ground. The ringin trip relay RT does not operate over this clrcuit due to the combined high resistance of the call bell and condenser of the substation D which prevents the flow of sufficient current to operate said relay RT. The call bell or the substation D will continue to be intermittently rung until the subscriber thereat removes his receiver and should he do so during a ringing period, the closure of the alternate switchhook contact-s permits suflicient current to flow through the winding of relay RT to energize it causing relay RT to close its alternate contact 32, thus establishing an energizing circuit for the ringing control relay RC traced from battery, winding of said relay RC, line 33, alternate contact 32 of relay RT to ground, relay RC then looking up through its alternate contact 27, and alternate contact 18 of relay CS'to ground. Relay RC operatingopens its normal contact 28 thus opening the circuit of interrupter relay IR- which is instantly prevented from further operating to connect ringing current to the called substation D. Should the subscriber at substation D remove his receiver during a non-ringing or silent-period, supervisory relay SR will energize to open its normal contact 34 to prevent the pre mature lightingof the lamp CL and to close its alternate contact 34 to close an energizin circuit for the ringing control relay RC Thesupervisory relay SR energizes over a circuit traced from battery upper winding of relay SR, cord conductor 3, alternate contacti26 of relay BT, normal contact 31 of relay IR, tip contacts of plug CP and jack J, through the alternate contacts ofithe now raised switchhook of the called substation D, ring contacts of plugCP and jack J, normal contact 30 of relay IR, cord conductor 4, alternate contact 22 of relay BT to ground through thelower winding of relay SR. Relay RC energizing over a circuit extending from battery, winding of said relay RC, alternate contact 34 of relay SR to ground, locks itself up through its alternate contact 27 i to ground through alternate contact 18 of relayC'S, tJhusopening the circuit for the interrupter relay IR at normal contact 28 of said relay RC to prevent the further application of ringing currentto the called substation l) as hereinbefore described. Thus I provide a system wherein ringing current is automatically and intermittently connected to the called telephone line and automatically disconnected upon the removal of the'receiver from the switchhook at the called substation D whether it'be during'a ringing period or a non-ringing period. i

The subscribers at substations A and=B are now in conversational circuit, which may be traced over the heavily marked lines. f a

Assuming that the subscribers A and B have fiDlSlleCl' their conversation, the subscriber at substation A replacing the receiver upon the switchhook, opens the energizing circuit of the supervisory relay AT at the switchhook cont-acts of substation A, which restoring closes its normal contact 35Zthus causing the clamp AL to light over a circuit traced from battery, throughthe said lamp AL, normal contact 35 of relay AT, alternate contact 9 of relay AS to ground, but lamp CL does not light because relay SR is now operated. The subscriber at substation VD replacing his receiver upon the switchi so the multiple jacks J and J whereupon the apparatus of the cord circuit is returned to its normal position. "Assuming now that the multiple jack J has abusy potential placed thereon, due to another cord circuit being connected to one of the multiple jacks J. of the called line, the operator inserts the calling plug GP into another multiple jack J of the same line, and relay CS will energize over the same circuit as before traced butthe busy test relay-BT of the cord circuit C will not operate since the busy'test relay of the first cord already connected to one of-themultiple jacksJ has operated, shunting out its upper h1gh reslstance winding and closing a low resistance locklng circuit for itself which is in multiple with the high resistance windingof relay RT of the second cord, thuspreventing the flow of suflicient current to energize the said relay BT of the second cord' circuit. 'Relay BT failing to. energize busy. back connecting relay BC will operate to connect the busy back signals BB to the calling substation A over a circuit traced from battery, winding of relay BC,normal contact 25 of relay BT, line 36, alternate contact 18 of relay CS to ground whereupon relay BC energizing closes a locking circuit for itself traced from battery, winding and alternate contact 20 of relay BC, sleeve contacts of plug GP and jack J to ground through out off relay C0 of line circuit L. The busy-back signaling current may be traced from battery B, through the interrupter I of the busy-back signal BB. through the'winding a of the induction coil c to ground. This'current will be induced into the'other winding 7) of the induction coil 0 and will flow through alternate contact 21 of relay BC,- line 37, conductor 3, alternate contact-8 of relay AS, tip contacts of plug APand jack Jythrough the receiver of the substation A,=ring contacts of plug AP and jack 'J, alternate1contact'13 of relay AS,

con ductor t, to ground through the lower winding of -relay'AT. It is obvious that ringing current will not be connected to the called line since relay BT failing to operate no circuit isclose'd for the interrupter relay IR. i Theisubscriber at the substation hearing the busy-back signal will know that the called line is busy and will replace the receiver upon the switchhook, thus opening the circuit of the supervisory relay AT at the switchhook contact-s causing said relay .AT to restore to close its normal contact 35,

whereupon lamp AL will light over a circuit traced from battery, through said lamp AL, normal contact 35 of relay AT, alternate contact 9 of relay AS to ground. The relay AT restoring closes an energizing circuit for the relay RC traced from battery through the winding of'relay RC, conductor '50, alternate contact 17 of relay"CS, conductor51, normal contact 35 of the relay AT,--to ground at alternate contact 9 of relay AS. Relay RC energized over this circuit, andthe closing of its alternat contact 29 lights the calling supervisory lamp traced from battery through said lamp CL, alternatecontact 29 to-ground at normal contact 34 of relay SE, The operator noting the two burning lamps knows that theconnection'is no longer required and will withdraw the plugs AP and CP from the multiple jacks J and J causing the apparatus to return, to its normal position.

Should, the calling subscriber hang up before the called subscriber answers, the relay will be energized through back Contact 35 of relay AT. Relay RC energizing locks, itself to ground at contact 18 of relay OS. A further result due to the enerbefore inserting the calling plug into a multiple jack of the, called line, but on the contrary she will, insert the calling plug into the calling jack, and should the line be busy the ringing current is. prevented from being connected to the called line, and an audible busy back signal is at once received by the calling subscriber. It is further seen'that I have arranged a system wherein no ringing key to be operated by the operator is provided,-but that ringing current is automatically, intermittently and instantly connected to the called line provided it is idle and free from busy poten- .-.AlthoughI have'shown a preferred embodiment of my invention for the purpose of illustrating and describing my invention, I do not .wish ,to be limited to the exact structure shown, as many. modifications and changes may be made by those skilled in the art, butaim to cover all such changes and modifications as come within the spirit-and scope of the appended'claims.

Having described my invention what I claim asnew and desire to secure by Letters Patenti's: I I

1. 'A telephone systemincluding busy and idle telephone lines, an operators cord circuit having an answering end and a calling end, a pair of relays one for each end, of said cord circuit, means for energizing said relays respectively when their respective ends of said cord circuits are connected to idle lines, and preventing their energization when connected to busy lines. busy back means automatically: connected to' said answering end when said calling end is connected toa busy line,- and telephonic translink circuit provided Withbusy-back means and ringing means normally disconnected from sa1d link circuit, a pair of electromagnets associated.withthecalhng end'of sa1d circuit, the one disconnecting the operators telephone set whenconnection is made to a called for line whether idle or busy, the other'magnet having a high and low resistance winding and sensitive to the idle or busy condition of the called. for line to effeet the connection of said busy back appara tus or said ringing apparatus according as the line is busy or idle.

3. A telephone system including idle and busy telephone lines, an operator controlled link circuit having apparatus at its calling end to automatically send abusy signal to the calling subscriber when said circuit is connected to a busy called line and control the connection of ringing current to an idle called line when said circuit is connected thereto, a calling supervisory signal for said link circuit, means for preventing a change in its normal indication when the called subscriber answers, and for changing its indication when he replaces his receiver.

4. A telephone system including idle and busy telephone lines, an operator controlled link circuit, having busy test apparatus associated with its calling end and serving to automatically extend a busy signal to a calling subscriber when said circuit is connected to a busy line or to automatically apply ringing current to an idle called line, a pair of supervisory signals for said operator for control by the calling and called subscribers respectively, and means for preventing the display of either supervisory signal while said busy signal is being received or said ringing current is being applied and said called subscribers receiver is off its switchhook.

5. A telephone system including idle and busy telephone lines, and an operator controlled link circuit adapted for connection to a terminal of a busy line and when so connected serving to automatically extend a busy signal to the calling line without signaling said operator, and a pair of supervisory signals for said operator, both sa1d signals having their indications changed by the calling subscriber replacing h1s receiver in response to said signal.

6. An operator controlled link circuit hav ing a terminal serving when connected to a busy called line to actuate mechanism to extend a busy signal to a connected calling subscriber without signaling said operator,

orwhen connected to an idle called line to automatically extend ringing current to the idlecalled line without any further work on the part of the operator, a pair of supervisorysignals inert while said signals are beingreceived and lighted when said calling subscriber replaces his receiver in re-. sponse to said busy signal and automatic means for connecting the operatorin conversational circuit with-the calling line.

7. A telephone system including an operator controlled link circuit and a calling supervisory signal therefor, a relay for said circuit energized by thev replacing of the Per. ceiver at a calling substation on failure to secure a response, said relay also energized by a response at the called substation, and mechanism controlled by said relay for displaying. said signal. V a

8. A'telephone system including an operator controlled link circuit and a supervisory signal for said operator, a relay adapted to assume a certain operative condition 'onthe replacing of the receiver at the calling substation, and the same condition on. removal of the receiver at the called substation, said relay controlling said signal, and automatic means actuated on connection of said link, circuit with a busy called line to signal the calling substation. e I

9. A telephone system including telephone lines, an operator controlled linkcircuit connected to a calling line, a pair of supervisory signals for said circuit, busy test apparatus for the calling end of said circuit effective on its connection to a busy line to automatically transmit a busy indication to the calling station, and means eliective by the replacing of the receiver at the calling station to change the indications of both said supervisory signals.

10. A telephone system including a pair of connected telephone lines, a relay controls ling the application of ringing current, said relay energizing and locking by the response of the called subscriber or by the replacing of the receiver at the calling substation whichever occurs first, and a supervisory signal circuit controlled by said relay.

11. A telephone system including a pair of telephone lines interconnected by an operator controlled link circuit, a pair of supervisory signals and means preventing the display of either when the calling station receiver is off the hook and the called station receiver is on the hook, and prior to the response at the called station, test apparatus efi'ective automatically on connection with the called line to transmit a busy signal to the calling station or a call signal to the called station according to the busy or idle condition of the connected called line, automatic means for automatically connecting the operator to the link circuit and in conversational circuit with the calling telephone said relay, another supervisory relay efi'ec-' line','and a pair of relays for said link circuit for preventing otherlink circuits from being operatively connected to the same lines interconnected by said link circuit.

' 12. I An o erators link circuit havin a re- P v a:

lay for energization to disconnect ringing current from said link, a supervisory relay efi'ectlve on its de-energization to energize said first mentioned relays andcontrolling their circuits, means for operating said pair of relaysrespectively over circuits of fixed resistance, and upon their operation altering theresistance of their circuits. 7

14. In a telephone system including telephone lines, a link circuit for connecting to said lines, busy tone apparatus, ringing apparatus, a relay adapted to energize when said link circuit is connected to an idle called line to automatically and intermittently apply ringing current to said connected line, said relay non-responsive when connection is made with a busy called line,

of September, 1921.

whereby said busy tone apparatus is connected in circuit with the calling subscriber from being operatively connected to said lines interconnected by said link circuit.

15. In a telephone system including tele-r phoneilines, a link circuit for interconnecting the same, a busy tone device and automatic ringing means for said'lin'k circuit, a double-wound relay responsive when said link circuit is connected to an idle called line to operate said ringing means to applyringing current to the called line, a singlewoundrelay responsive when connection is made with a busy called line to connect said busy tone device in circuit with the calling subscriber to inform him'of the busy condition of said busy calledline, said d0i1ble-- wound relay remaining inert when connection is made with a busy called line, and a pair of relays for said link circuit for preventing other link circuits from being operatively connected to said lines interconnected by said link circuit, said double woundrelay comprising one of said relays. Signed by me at Chicago, in the county of- Gook and State ofIllinois, this 16 day,

LEROY DI KELLOGG'. 

